KNES 351 Lecture Notes - Lecture 13: Cardiac Arrest, Sympathetic Nervous System, Parasympathetic Nervous System
Document Summary
Sa node dictates the rhythm of heart and wants to do so at 100-120 bpm: however, resting heart rate is 50-60 bpm, resting heart rate is brought down by constant parasympathetic nervous system activation. Through the vagus nerve, the heart receives acetylcholine which decreases heart beats per minute (slows the heart rate down). To go to sleep, the body increases pns output; there is an increase in secretion of acetylcholine. Exercise places a lot of load in the heart: the heart is constantly being placed under stretch (blood fills the heart a lot and really fast) and constantly contracts a lot of blood, really fast. Exercised induced cardiac hypertrophy results in hypertrophy of fibers outward; the chamber size remains the same but because the ventricle has larger muscle, the heart does not pump as hard to pump the same amount of blood.
